Flow control valves of the type having a liquid pressure actuated diaphragm to control opening and closing of the valve have long been known in the art. Typically, such valves include a means for bleeding liquid pressure from the inlet side of the valve to a control chamber where the liquid bled from the inlet acts on the diaphragm to maintain the valve closed, a pilot valve being provided to relieve the pressure in the control chamber to effect opening of the valve. However, these valves were not provided with an anti-syphon device such as disclosed herein. Similar control valves are shown in U.S. Pat. No. 3,591,126, U.S. Pat. No. 4,081,171, U.S. Pat. No. 4,105,186, U.S. Pat. No. 4,135,696 and U.S. Pat. No. 4,180,236. These patents in turn refer to other valve assemblies.